Targeting microbial quorum sensing: the next frontier to hinder bacterial driven gastrointestinal infections

In vitro inhibition of Pseudomonas aeruginosa PAO1 biofilm formation by DZ2002 through regulation of extracellular DNA and alginate production

Introduction

Pseudomonas aeruginosa (P. aeruginosa) is a common pathogen associated with biofilm infections, which can lead to persistent infections. Therefore, there is an urgent need to develop new anti-biofilm drugs. DZ2002 is a reversible inhibitor that targets S-adenosylhomocysteine hydrolase and possesses anti-inflammatory and immune-regulatory activities. However, its anti-biofilm activity has not been reported yet.

Methods and results

Therefore, we investigated the effect of DZ2002 on P. aeruginosa PAO1 biofilm formation by crystal violet staining (CV), real-time quantitative polymerase chain reaction (RT-qPCR) and confocal laser scanning microscopy (CLSM). The results indicated that although DZ2002 didn't affect the growth of planktonic PAO1, it could significantly inhibit the formation of mature biofilms. During the inhibition of biofilm formation by DZ2002, there was a parallel decrease in the synthesis of alginate and the expression level of alginate genes, along with a weakening of swarming motility. However, these results were unrelated to the expression of lasI, lasR, rhII, rhIR. Additionally, we also found that after treatment with DZ2002, the biofilms and extracellular DNA content of PAO1 were significantly reduced. Molecular docking results further confirmed that DZ2002 had a strong binding affinity with the active site of S-adenosylhomocysteine hydrolase (SahH) of PAO1.

Discussion

In summary, our results indicated that DZ2002 may interact with SahH in PAO1, inhibiting the formation of mature biofilms by downregulating alginate synthesis, extracellular DNA production and swarming motility. These findings demonstrate the potential value of DZ2002 in treating biofilm infections associated with P. aeruginosa.

Salmonella infection acts as an environmental risk factor for human colon cancer

Emerging evidence has demonstrated that perturbations of host-microbial interactions by pathogens can lead to an altered microenvironment that promotes tumorigenesis. A recent study provides new evidence and mechanisms on how repetitive exposure to non-Typhoidal Salmonella (NTS) increases the risk for colon cancer. This study integrated a serological and epidemiological approach with both in vivo and in vitro analyses, showed that the magnitude of exposure to NTS is associated with colonic tumorigenesis. In vivo exposure to repetitive low doses of NTS led to colonic tumors similar as a single high NTS dose in mice. Repetitive NTS infections significantly increase the proliferation of transformed cells in tissue cultures. The research results open new possibilities for the diagnosis, prevention, and treatment of colon cancer. The unanswered questions remain, including validation of the current findings in other cohorts, differences in lifestyle, and changes of gut microbiome after Salmonella infection. Salmonellae exposure can be limited by eating cooked meats and washing vegetables well. It is necessary to develop guidelines and criteria for screenings and follow-ups in people with exposure history to Salmonella and other cancer-associated pathogens.